Electro-hydraulic actuating cylinder



' Filed Sept. 6, 1955 1959 v M. w. MARIEN 2,918,795

ELECTRO-HYDRAULIC ACTUATING CYLINDER 2 Sheets-Sheet 1 24 32 3s 35 as 2623 1512.1

MELVIN W. MARIEN AT TO N EYS INVENTOR.

M. W. MARIEN ELECTRO-HYDRAULIC ACTUATING CYLINDER 2 She ets-Sheet 2Filed Sept. 16, 1955 vwww mo wwm mo INVENTOR.

MELVIN W. MARIEN BY 1%,, 7M A#e%- TORNEYS United States PatentELECTRO-HYDRAULIC ACTUATING CYLINDER Melvin W. Marien, Brentwood, Mo.,assignor to Ramsey Corporation, a corporation of Ohio ApplicationSeptember 6, 1955, Serial No. 532,672

2 Claims. (Cl. 6052) This invention relates to an actuating mechanism,and more particularly to a self-powered hydraulic unit or fluid motor,and still more particularly to an electrohydraulic actuating cylinderfor use as a window opener, a door opener, in power steering, foraircraft controls and flaps, or wherever a remote or otherwise push-pullaction is desired, although other uses and purposes may be apparent toone skilled in the art.

Heretofore, where fluid motors, such as hydraulic cylinders, have beenemployed for use in providing a remotely controlled push-pull operation,it has been necessary to position the pressurized fluid supplying means(prime mover and pump) at a distance from the hydraulic cylinder. Suchan installation required long pressure tubes between the fluid pump andhydraulic cylinder which reduced the overall efliciency of the unit. Inthe past, to eliminate the long pressure tubes, the hydraulic actuatingcylinder has, in many cases, been remotely positioned from the job andconnected thereto by mechanical linkages which also reduce the overallefliciency of operation. Where long pressure tubes and mechanicallinkages have been employed in a hydraulic system, it has been foundthat such arrangements are quite cumbersome and require a large amountof protected space. Moreover, failure in operation of a hydrauliccylinder or in the desired push-pull operation is extremely hazardousdue to the possibility of leakage along the long pressure tubes orbreakdown along a mechanical linkage.

In accordance with the invention, a complete hydraulic system isprovided in a single package. A common housing encloses a cylinder andpiston, a fluid reservoir, a fluid pump communicating with both sides ofthe piston, and an electric motor. Suitable check and relief valvearrangements are provided to prevent any undue pressure built up at eachend of the cylinder and to compensate for the reduced volume at the endof the cylinder connected to the piston rod.

In the preferred embodiment, the pump and electricmotor are carried bythe piston, While in another embodiment the pump and electric motor arestationarily positioned at one end of the cylinder.

It is then an object of this invention to provide a Another feature ofthis invention resides in the provision of an electro-hydraulicactuating cylinder which eliminates the necessity of providing longpressure tubes between the cylinder and source of pressurized fluid, and

eliminates the necessity of having mechanical linkages thasst- 2,918,795I Patented Dec. 29, 1959 connecting the actuating piston with theelement desired to employ the push-pull movement.

Another object of this invention is to provide an electro-hydraulicactuating cylinder having a common housing enclosing a double-facedpiston slidable in a cylinder, a fluid reservoir, and a pump-motor unitcarried by the piston, wherein it is only necessary to connect thecylinder to a source of electricity for operation.

A still further object of this invention is to provide anelectro-hydraulic actuating cylinder having a common housing enclosing acylinder and a double-faced piston slidable therein, a fluid reservoir,and a pump-electric motor assembly stationarily positioned at one end ofthe housing, wherein it is only necessary to connect the cylinder to asource of electric power for operation.

Other objects, features, and advantages of the invention will beapparent from the following detailed disclosures, taken in conjunctionwith the accompanying sheets of drawings, wherein like referencenumerals refer to like parts, in which, on the drawings:

Figure 1 is a longitudinal sectional view, with parts in elevation, of ahydraulic cylinder constructed in accordance with the principles of theinvention;

Figure 2 is a transverse sectional view, taken substantially along theline IIII in Figure l and looking in the direction of the arrows; and

Figure 3 is a longitudinal sectional view, with parts in elevation, of ahydraulic cylinder illustrating a different form of the invention.

As shown on the drawings:

In the preferred embodiment as seen in Figure 1 and Figure 2, thehydraulic actuator 10 includes a common housing 11 that encloses apiston cylinder 12, a doublefaced piston assembly 13 slidable in thecylinder, and an annular fluid reservoir 14. The piston assembly 13carries an internal gear pump 15 and an electric motor 16, preferably ofthe induction type.

The housing 11 includes an outer cylindrical shell 17 concentricallypositioned with respect to the cylinder 12. The shell 17 and cylinder 12are closed at each end and held in properly spaced relationship by arear end head 18 and a front end head 19 in abutting relationship withan end plate 20. A series of annularly arranged elongated nut and boltassemblies 21 interconnect the end heads 18 and 19 and the end plate 20.It is noted that an annular shoulder 18a on the end head 18, and anannular shoulder 19a on the end head 19 extend inwardly between theopposite ends of the cylinder 12 and the shell 17. An anchoring lug 1812projects outwardly from the end head 18 to provide means for attachingthe housing 11 to any desired structure.

It is noted that the space between the cylinder 12 and shell 17 definesthe annular fluid reservoir 14 which is vented at 14a. Any desirablehydraulic fluid may be employed for use in the instant invention.

The piston 13 is relatively elongated and divides the inside of thecylinder 12 into a rear power or fluid chamber 22 adjacent the rear endhead 14 and a front power or fluid chamber 23 adjacent the front endhead 19. The piston 13 comprises a cylindrical member 24 diametrallysize to be freely slidable Within the cylinder 1.2 closed at one end bya disk-shaped wall 25 that is suitably secured thereto. The wall 25 isprovided with an annular notch 25a for receiving a resilient packing cup26. The packing cup 26 may be of any suitable material, such as rubber,leather, etc., and is held in position by a retainer 27 suitably securedto the wall 25, such as by stud bolts or the like (not shown). Theretainer 27 is centrally bored and carries a flat circular wall 27a atone end thereof, and a hollow piston rod 28 at the other end The pistonrod 28 extends through a centrally disposed aperture in the front endhead 19 and end plate 20, and terminates in a connecting lug 28a. Theend head 19 is suitable recessed at the outer end to provide an annularspace for a plurality of resilient packing rings 29 for providing a sealaround the piston rod 28. A rigid ring 30 overlies the packing rings 29and is held in place by the abutting end plate 20.

The rear end of the piston 13 is closed and is provided with a dividingwall 31 received within the cylinder member 24 and secured thereto, suchas by press fitting. The wall 31 is spaced from the end of the cylinder24 by a spacing ring 32, the outer face of which is in planar alignmentwith the peripheral edge of the member 24. A resilient packing cup 33abuts the end of the cylindrical member 24 and a portion of the spacingring 32, and is secured thereto by a disk-shaped retainer 34. Thepacking cup 33 may also be constructed in a similar manner as-thepacking cup 26. Stud bolts (not shown) or other suitable fasteners maybe employed to secure the re tainer 34 to the spacing ring 32. Hence,the piston 13 is double-faced and is divided between its ends by thewall 31 to define a pumping chamber and a motor chamber, the motorchamber being adjacent the piston rod end of the piston.

The motor 16 is received in the motor chamber and is preferably of thereversible induction type. The motor 16 comprises a stator 35 suitablysecured to the inner wall of the cylindrical piston member 24, and arotor 36. The rotor is carried on a shaft 37 that is bearingly supportedby the packing cup retainer 34, the dividing wall 31, and the end wall25. The stator 35, while more or less diagrammatically illustrated, isof such design, such as having a plurality of windings, as to render theelectric motor 16 reversible.

Electric wires leading to the stator extend through the disk-shaped wall25, the closing plate 27a, and the hollow piston rod 28 to terminals onthe attaching lug 28a. It may be noted that the rotor 36 is diametrallysized as to be slightly spaced from the stator 35 thereby providing anannular passageway therebetween as indicated by the numeral 38.Moreover, the rotor 36 is of such width as to be spaced from thedividing wall 31 on one end and the disk-shaped wall 25 at the other endas to provide annular passageways around the shaft 37.

To supply pressurized fluid to the power chambers 22 and 23, theinternal gear pump 15 is provided having an impeller 39 in meshingengagement with a rotary internal gear 40, as more clearly seen inFigure 2. The impeller 39 is suitably secured to the shaft 37 such as bythe key 39a. Thus, the rotor 36 of the motor 16 is directly connected tothe impeller 39 of the pump 15. The spacing ring 32 functions as thebody of the internal gear pump 15, and the impeller 39 is mountedeccentrically with the body and actuates the internal gear 40 rotating.in the body or ring 32.

The pump 15 is provided with a pair of combination inlet-outlets 41 and42 which are formed in the abutting side plates, in this case, thedividing wall 31 and the retaining member 34, respectively. Eachinlet-outlet is in the form of an arcuate slot and diametrically opposedwith respect to the impeller 39. The inlet-outlet 41 communicates withthe front power chamber 23 through the passageway 38 defined by therotor and stator of the motor 16 and a passageway 43 extending throughthe wall 25 and retaining member 27, while the inlet-outlet 42communicates with the rear power chamber 22 through a suitable alignedopening in the retaining member 34.

When the electric motor 16 is driving the pump 15 in the directionindicated by the arrows 44 in Figure 2 the fluid flow will be from thepower chamber 23 to the power chamber 22, thereby permitting theinlet-outlet 41 to function as an inlet to the pump 15, while theinletoutlet 42 functions as an outlet. Fluid will be drawn through thepassageway 43, the passageway 38 between the rotor and stator of themotor 16, through the pump 15 and into the power chamber 22. It isunderstood that the rotor 36 and the stator 35 of the motor 16 will beso protected with insulation as to prevent these elements from beingdamaged or effected by the hydraulic fluid flow. In other words, therotor and stator of the motor 16 will be at all times in fullcommunication with the fluid flow between the power chambers 22 and 23.

Inasmuch as the volume of the power chamber 23 is much less than thevolume of the power chamber 22 due to the piston rod 28 extendingthrough the chamber 23, additional fluid is received from the reservoir14 by the power chamber 23 through a conduit 45, a check valve 46 whichallows unidirectional flow from the reservoir 14, a conduit 47interconnecting the valve 46 with the end head 19, and a curvedpassageway 48 in the end head 19 intercommunicating the conduit 47 withthe power chamber 23. While the check valve 46 may be of anyconventional type, it is merely illustrated diagrammatically inFigure 1. If the fluid pressure in the power chamber 22 exceeds apredetermined amount, an adjustable relief valve 49 will open and allowfluid flow to the reservoir 14. The valve 49 is connected to thereservoir 14 through a tubular section 50 and intercommunicates with thepower chamber through a bent piece of tubing 51. With fluid flow intothe power chamber 22, the piston 13 will, of course move toward thefront end head 19, thereby extending the hydraulic unit 10.

In reversing the direction of the pump 15 and the motor 16, fluid flowwill be established from the power chamber 22 to the power chamber 23.In order to compensate for the smaller fluid capacity in the chamber 23,excess fluid will be returned to the reservoir 14 through the passageway48, the conduit 47, and the conduit 45 through a conduit 52, anadjustable relief valve 53, and a conduit 54 connecting in the conduit45. During this operation, the inlet-outlet 42 performs as an inlet,while the inlet-outlet 4-1, performs as an outlet in connection with thepump 15. And again the fluid flow will pass between the rotor and statorof the motor 16, and through the passageway 43. In filling the powerchamber 23 and emptying the power chamber 22, the piston 13 will, ofcourse, move towards the rear end head 18 thereby retracting thehydraulic unit 10.

It will be understood that the check valve 46 and the relief valves 49and 53 perform as unidirectional flow valves and may be of anyconventional type for the intended purpose. These valves and associatedtubing intercommunicating the power chambers with the reservoir are moreor less illustrated diagrammatically for clarification purposes, but itis understood that these elements will in all probability be confinedwithin the common housing 11. For example the valves 46 and 53 and theirassociated conduits may easily be confined within the end head 19.

Now referring to Figure 3, a self-powered hydraulic unit 60,illustrating a different form of the invention, includes generally ahousing 61 enclosing a fluid cylinder 62, a piston 63 slidable in thecylinder, a fluid reservoir 64, an internal gear pump 65, and anelectric motor 66.

The housing 61 includes a cylindrical shell 67 closed at one end by arear end head 68, and at the other end by a front end head 69. An endplate 70 abuts against the outside wall of the end head 69 and carries adepending flange 70a for mounting the housing 61. The end heads 68 and69 are annularly notched at 68a and 69a to receive the opposite ends ofthe cylindrical shell 67. A plurality of annularly arranged nut and boltassemblies 71 hold the end heads 68 and 69 and the end plate 70 intightly abutting relationship.

A disk-shaped dividing wall 72 is intermediately positioned between theends of the cylindrical shell 67 di viding it into two sections. Thewall 72 carries an enlarged integral annular ring section, the outerperiphery of which is snugly received by the inner wall of thecylindrical housing member 67. The ring section coacts with the mainsection of the wall 72'to define a pair of aligned annular shoulders 72aand 72b.

The shoulder 72a receives one end of the fluid cylinder 72, while theother end of the cylinder is received by a shoulder 69b formed in thefront end head 69 thereby concentrically disposing the cylinder 62 withrespect to the cylindrical housing member 67. One end of a cylindricalshell 73 is received by the shoulder 72b of the dividing wall 72, whilethe other end of the shell is received by an annular groove 68b in theend head 68. The shell 73 is axially aligned with respect to thecylinder 62 and together define along with the cylindrical housingmember 67 the annular fluid reservoir 64. The reservoir is vented at64a. Also, the shell 73 serves as an enclosure for the motor-pump unit.

The compartment defined by the cylinder 62, the end head 69 and thedividing wall 72 comprises the cylinder section of the hydraulic unit60, and is divided into a pair of power chambers 74 and 75 by the piston63. The piston 63 includes a center disk member 76 freely receivedwithin the cylinder 62 and serving as a spacer for a pair of oppositelyfacing packing cups 77 and 78. The packing cups, of course, sealinglyengage the inner wall of the cylinder 62 and are secured to the spacer76 by retainer members 79 and 80, respectively. The spacer 76 and theretainer 80 are centrally apertured, and the retainer 79 is centrallytapped to receive one end of a piston rod 81. The piston rod 81 carriesan annular flange 81a which abuts against the retainer 80, and the rodis threaded at the very end to be received in the tapped retainer 79.When the rod 81 is drawn up tight against the retainer 80, theretainers, the spacer and packing cups are held together as a unit.

The piston rod 81 extends through a suitably formed hole in the frontend head 69 and terminates in a threaded end 81b for connection to amechanism desired to have a push-pull movement. The rod receiving holein the end head 69 is radially enlarged at the outer side to receive aplurality of packing rings 82 to sealingly engage the piston rod. A ringmember 83 overlies the packing rings 82 and is held in place by the endplate 70.

Referring now to the motor-pump unit, the motor 66 includes a rotor 84rotatably mounted on a shaft 85, and a stator 86 suitably secured to theinner wall of the cylindrical shell 73. The shaft 85 is bearinglysupported at its opposite ends by the rear end head 68 and the dividingwall 72. The stator 86 is of a conventional type providing reversiblerotation of the rotor 84, and may be connected to a suitable electricsource by the leads 86a extending through the rear end head 68.

The pump 65 is a conventional internal gear pump and includes a sideplate 87 and the dividing wall 72 that functions as a side plate, a bodymember 88 received within the cylindrical shell 73, an internal gear 89rotatably received within the body 88, and an impeller 90 eccentricallymounted with respect to the body 88 and for actuating the internal gear89. The body, internal gear and impeller are received between the endplate 87 and the dividing wall 72. The impeller 90 is suitably securedto the shaft 85 by a key member 85a. It is to be understood that thepump 65 is substantially identical with the pump 15 of the embodiment inFigure 1 and Figure 2. The pump is provided with a pair of combinationinletoutlets 91 and 92 which are in the form of arcuate openings such asthe inlet-outlet 41 shown in Figure 2.

In operation, the hydraulic unit 60 will function in a similar manner asthe hydraulic unit 10. It may be noted that the pump inlet-outlet 92 isin direct communication with the power chamber 74, while the pumpinlet-outlet 91 communicates with the power chamber 75 through a radialgap 93 existing between the rotor and stator of the motor 66, apassageway 94 in the end head 68, a tubular member 95 supported at eachend by the opposite'end heads and intermediately by the enlarged ringsection of the dividing wall 72, a passageway 96 in the end head 69, andan annular port 96a opening into the power chamber 75. It is noted thatthe rotor 84 and stator 86 of the motor 66 are spaced at each end fromthe end head 68 and the end plate 87 of the pump 65 to provide annularfluid passageways. It is to be understood that the rotor and stator aresimilarly insulated as the rotor and stator 36 and 35 of the electricmotor 16 in the embodiment shown in Figure 1 as to preclude damage orinjury thereby due to the fluid flow therearound. At all times the rotorand stator are in full communication with the fluid flow from the pump65.

When it is desired to shorten the hydraulic unit 60 or retract thepiston rod 81, the motor and pump are rotated in the direction to pumpthe fluid from the power chamber 74 and into the power chamber 75.During this operation, the inlet-outlet 92 will function as an inlet tothe pump 65, while the inlet-outlet 91 will function as an outlet.Pressurized fluid will flow through the pump 65, the gap 93 between therotor and stator of the motor 66, the passageway 94, the tubular member95, the passageway 96, and the port 96a. Since the volume of thepressure chamber 75 when the piston 63 is fully retracted is less thanthe volume of the power chamber 74 when the piston rod 81 is fullyextended, excess fluid will be returned to the reservoir 64 through apassageway 97 in the end head 68 into a duct 98a of a valve housing 98,through an adjustable pressure relief valve or unidirectional valve 98binto a return duct 98c, andthrough a return passageway 99 in the endhead 68.

In order to extend the hydraulic unit 60 and protract the piston rod 81,the direction of the motor and pump is reversed to draw the fluid fromthe power chamber 75 and pump it into the power chamber 74, wherein thepressurized fluid will exert a pressure against the end of the piston 63to move the piston towards the end head 69. During this pump operation,the inlet-outlet 91 functions as in inlet to the pump 65, while theinlet-outlet 92 functions as an outlet. The fluid will then flow fromthe power chamber 75 into the power chamber 74, and inasmuch asinsuflicient fluid in contained in the power chamber 75 to fill thepower chamber 74, additional fluid is taken from reservoir 64. Thisadditional fluid passes through the passageway 99 in the end head 68,the duct 98c in the valve housing 98, a unidirectional or check valve98d, the duct 98a, the passageway 97 in the end head 68, and through therotor-stator gap 93 to the inlet 91 of the pump 65.

In view of the foregoing, it is seen that an electrohydraulic actuatingcylinder is provided which is decidedly compact in size, is operable inany installation upon connection to a source of electrical energy, andis highly eflicient due to'the elimination of long pressure tubes andlinkage assemblies.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention, but it is understood that this application is to be limitedonly by the scope of the appended claims.

I claim as my invention:

1. A self-powered hydraulic unit comprising a casing having a pair ofconcentric cylindrical members and an end head at each end thereof, afluid reservoir defined between the concentric members, a double-facedpiston slidable within the inner cylindrical member and having a pistonrod extending through one of the end heads, a pump and electric motorassembly carried by the piston, said pump having a first inlet-outletleading to one side of the piston, a second inlet-outlet leading to theother side of the piston, a separate line intercommunicating each sideof the piston with the reservoir, an unidirectional valve in each linepermitting fluid flow towards the reservoir, a bypass line around saidvalve serving the piston rod side of the piston, and a secondunidirectional valve in said bypass line preventing the fluid flowtherethrough towards the reservoir.

2. A self-powered hydraulic unit comprising a casing having a pair ofconcentric cylindrical members and an end head at each end thereof, areservoir defined between the concentric members, a double-faced pistonslidable within the inner cylindrical member and having a piston rodextending through one of the end heads, a pump and electric motorassembly carried by the piston, said pump having a first inlet outletleading to one side of the piston, 21 second inlet-outlet leading to theother side of the piston, a separate line intercommunicating each sideof the piston with the reservoir, means in each line preventing thereturn flow of fluid to the respective piston sides, a bypass linearound the means serving the piston rod side of the piston, and means insaid bypass line preventing the fluid flow therethrough towards thereservoir.

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